1. Field of the Invention
The present invention relates to a universal motor having a commutator, at least two carbon brushes electrically contacting the commutator in respective commutation regions, a ventilation device for producing a cooling flow in a cooling flow path, and dust protection means for preventing penetration of material particles such as dust and the like, in particular, produced during operation of a hand-held power tool, into the commutation region and including at least one guide member that provides for delivering of the material particles in the cooling flow.
2. Description of the Prior Art
In universal motors of the type discussed above, the commutation regions are protected by the dust protection means from the erosion action of the material particles, which increases the service life of the motors.
U.S. Pat. No. 6,097,128 discloses a universal motor with two carbon brushes held in respective brush guides. Hood members are pushed over the brush guides, around the carbon brushes, forming a partially closed chamber. To remove the carbon dust, which is carried from the carbon brushes, an air flow from the chamber and into the cooling air flow is produced by providing flow openings in the hood members, with the air flow carrying away the dust laden air.
The drawback of the known universal motor consists in that the guide members, which are formed by hood members, have a relatively complex construction, which involves additional manufacturing costs. In addition, the provided dust protection means is not suitable for removing large amounts of material particles from the commutation region, which are produced when, e.g., hand-held power tools, in particular drills or chisel tools are used. This is because of high flow losses within the guide members and a rapid dust deposition.
Accordingly, an object of the present invention is to provide a universal motor in which the drawbacks of the known universal motor are eliminated.
Another object of the present invention is to provide a universal motor in which a better removal of material particles from the commutation regions is achieved, together with reduction of additional costs associated with dust removal.